Networking problem, Please help?

Ok so here's how it all started. I have this router, Linksys model

WRT150N. Next, I have 1 desktop computer, and 3 laptops. So I installed it on the desktop and later when i tried to install Vista on the desktop so I guess Linksys was deleted but the internet still worked on all computers so i left it at that. Then I found that Vista sucked and re-installed windows xp, the internet still worked. Just recently I decided to re-install Linksys on the desktop again because I wanted to change a few settings. It ended up re-creating the entire network, now the problem is that, I can get on the computer with the desktop. The lights on the Router for Internet and Wireless are lit. Except it says that the router can not connect to the internet and the laptops can't connect to the router (Even after i changed all their settings to have the new pass key). If any one knows what the problem might be and how to fix it I would greatly appreciate the help.Thanks